The presence or absence of BlsA, a protein with a blue light-sensing flavin domain in the genomes of Acinetobacter species has aroused curiosity about its roles in the regulation of bacterial lifestyle under light. Genomic and transcriptomic analyses revealed the loss of BlsA in several multidrug-resistant (MDR) A. baumannii strains as well as the light-mediated induction of blsA, along with a possible BlsA-interacting partner BipA. Their direct in vivo interactions were verified using a bacterial two-hybrid system. The results demonstrated that the C-terminal region of BipA could bind to the C-terminal residues of BlsA under blue light at 23°C but not at 37°C. Genetic manipulations of blsA and bipA revealed that the coexistence of BlsA and BipA was required to induce the light-dependent expression of ompA in A. baumannii ATCC 17978 at 23°C. The same phenomenon occurred in the BlsA-deficient MDR strain in our functional complementation assay; however, the underlying molecular mechanism remains poorly understood. BlsA-modulated amounts of OmpA, the most abundant porin, in the outer membrane affected the membrane integrity and permeability of small molecules. Dark conditions or the deletion of ompA made the membrane more permeable to lipophilic ethidium bromide (EtBr) but not to meropenem. Interestingly, light illumination and low temperature conditions made the cells more sensitive to meropenem; however, this bactericidal effect was not noted in the blsA mutant or in the BlsA-deficient MDR strains. Light-mediated cell death and the reduction of biofilm formation at 23°C were abolished in the blsA mutant strain, suggesting multifaceted roles of BlsA in A. baumannii strains.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) (grant no. NRF-2020M3A9H5104237).
Copyright © 2023 Yang et al.
- BLUF domain
- bacterial two-hybrid system
- membrane permeability
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Modelling and Simulation
- Molecular Biology
- Computer Science Applications